Electric Driving Unit for a Vehicle

ABSTRACT

An electric drive unit for a motor vehicle includes an electric motor having a stator that is fixed with respect to a stub axle and a rotor that is rotatably supported with respect to the stub axle. A gear system has its input connected to the rotor for torque transmission. A wheel carrier is connected to the output of the gear system for torque transmission. A first bearing of the wheel carrier is provide on a first axial side of the electric motor facing away from the gear system. A second bearing of the wheel carrier is provided either on the first axial side of the electric motor, or in the gear system, realized in the form of a bearing of a rotatable gear system part connected to the wheel carrier.

Subject matter of the invention is an electric drive unit for a motorvehicle, comprising:

(a) a stub axle;

(b) an electric motor having a stator that is fixed with respect to thestub axle and having a rotor that is rotatably supported with respect tothe stub axle;

(c) a gear system having its input connected to the rotor for torquetransmission;

(d) a wheel carrier connected to the output of the gear system fortorque transmission;

characterized in

(e) that there is provided a first bearing of the wheel carrier on afirst axial side of the electric motor facing away from the gear system;

(f) and that there is provided a second bearing of the wheel carrier

-   -   either on the first axial side of the electric motor as well    -   or in the gear system, realized in the form of a bearing of a        rotatable gear system part connected (directly or indirectly) to        the wheel carrier.

Electric drive units for motor vehicles are already known. As examplesof electrically driven motor vehicles, the following may be indicated:scooter-like motor vehicles for standing on; scooter-like motor vehiclesfor sitting on; small vehicles, in particular for airports and golfcourts; motor vehicles of the type of passenger motor vehicles producedin millions of numbers, i.e. having typically one to seven seats and aroof; mini-busses and busses; trucks. The electric drive unit accordingto the invention is suitable in particular for all of these kinds ofmotor vehicles. For reasons that will still become clearer furtherbelow, the electric drive unit according to the invention is suited inparticularly good manner for applications in which high driving torquesor high driving powers for the motor vehicle are to be provided and forlarge/heavy motor vehicles. Examples in this regard are trucks and, inmore general form, heavy transport vehicles. To be named as particularlysuited vehicles are motor vehicles in which more than one or two motorvehicle wheels are driven by a respective electric drive unit, e.g.large/heavy transport vehicles with four or more driven wheels. Althoughthe electric drive unit according to the invention has been developedprimarily for installation in non-railbound motor vehicles, it may alsobe put to advantage for railbound vehicles.

In case of electrically driven motor vehicles, the question arising ishow the required electrical energy can be fed to the motor vehicle. Inparticular, the following possibilities are known: an accumulator fromwhich electrical energy for the drive unit can be withdrawn (e.g. ascooter with accumulator); generation of electrical energy on board ofthe vehicle (e.g. combustion engine with current generator on board ofthe vehicle; fuel cell stack on board of the vehicle); transfer ofelectrical energy from outside into the motor vehicle (e.g. bus withcurrent collector from an overhead line; railbound vehicle with currentcollector form an overhead line). The electric drive unit according tothe invention is suited in particular for all of these types of electricenergy connection.

It is emphasized that it is indeed preferred in the scope of theinvention to combine the drive unit with a motor vehicle wheelperforming a rolling motion on the ground or a rolling path. However,this does not necessarily have to be so. Rather, the wheel carrier mayissue its torque finally desired for driving the motor vehicle, to anycomponent related with the drive of the motor vehicle. All of this willbecome still clearer further below by way of concrete examples. Anyway,the term “wheel carrier” is not to be understood in a restrictive senseas a “carrier for a wheel rolling on the ground or a rolling path”.

There are known electric drive units for motor vehicles in which anelectric motor and a gear system are combined. In this regard, there areembodiments in the prior art in which the gear system is a planetarygear system.

It is the object of the invention to make available an electric driveunit for a motor vehicle, in which the electric motor and the gearsystem are combined in so favorable manner that there are advantagesarising in terms of the space required and/or in terms ofmounting/unmounting.

In the electric drive unit according to the invention it is provided,according to a first alternative, that the support of the wheel carrieris concentrated on the axial side of the electric motor directed awayfrom the gear system. As a consequence thereof, there are optimumprerequisites provided for axially mounting the electric motor and thegear system one after the other on the stub axle, permitting extremelysimple unmounting in the opposite direction and sequence, in particularin case of repair and maintenance works. The second alternativeaccording to the invention provides for savings in supportingexpenditure and space requirements. With a skilled design, there aresimilarly good mounting and unmounting conditions achieved as outlinedabove in connection with the first alternative. Preferably, the driveunit can be designed such that gear system and electric motor may beunmounted also without removal of the vehicle wheel, i.e. withoutjack-lifting of the vehicle.

In the electric drive unit according to the invention, the gear systempreferably is a planetary gear system comprising a sun wheel, planetwheels, a planet carrier and a ring gear. The planetary gear systempreferably has stepped planet wheels. A multi-stage planetary gearsystem is possible as well. Planetary gear systems provide for theadvantage that high torques can be transmitted with comparatively littlespace required and that high stepping up/down relationships can beattained. In case of the invention, the stepping ratios preferably arefrom higher speed to lower speed, corresponding to stepping ratios fromlower torque to higher torque.

In the drive unit according to the invention, the electric motor and thegear system preferably are arranged coaxially beside each other.

The afore-mentioned bearing of a rotatable gear system part preferablyis a bearing of the planet carrier. Looking at a planetary gear systemwith power take-off from the planet carrier, the planet carrier isjoined to the wheel carrier anyway. Besides, the planet carrier issupported for its rotary motion anyway so that one bearing is basicallysaved. It is preferred in this regard to introduce the radial wheelloads from the wheel carrier via the planet carrier and theafore-mentioned bearing of the gear system part into the stub axle andto design this bearing in accordance with the overall forces.

In case of the second alternative of the invention, it is preferred toprovide a common lubricant for the gear system and said bearing of arotatable gear system part. Such lubricant preferably is transmissionoil.

Due to the close combination of electric motor and gear system accordingto the invention, it is well possible and preferred that the rotor ofthe electric motor and the input of the gear system are joined to eachother without an intermediate compensating member. The support of therotor and the support at the input of the gear system are coupled interms of support on the stub axle so that an intermediate compensatingmember for compensating tolerances can be dispensed with here.

The wheel carrier preferably is designed in axially split manner. It isthus possible to leave a first axial part of the wheel carrier on thegear system when unmounting the same from the drive unit. This providesfor better accessibility to the other component parts of the drive unit.

Preferably, the gear system is designed to be unmounted from the driveunit in the form of a module (and, in assembly, to be mounted as amodule). This unmountability in the form of a module also is to coverthe case that a smaller remainder of the gear system (at first) remainson the drive unit when the main part of the gear system is unmounted.The module unmountability facilitates maintenance and repair works. Thegear system in its entirety can be replaced rapidly and easily. Uponunmounting of the gear system, the electric motor is rapidly and readilyaccessible. Preferably, the gear system module can be unmounted togetherwith one wheel carrier part.

The main part of the rotor of the electric motor, upon release from itssupporting portion, preferably is adapted to be unmounted from the driveunit in axial direction. The stator of the electric motor preferably isadapted to be unmounted from the drive unit in axial direction. Thepreferred unmounting possibilities “vice versa” provide for preferredmounting possibilities. The preferred unmounting and mountingpossibilities, respectively, of the electric motor, so to speak in twocomponent parts, without the necessity of unmounting the support properof the rotor, results in convenient and rapid unmounting and mounting ofthe electric motor for maintenance and repair works. As an alternative,it is preferred to provide for the possibility of unmounting theelectric motor in its entirety from the stub axle and mounting theelectric motor in its entirety to the stub axle, respectively.

Preferably, the first bearing of the wheel carrier has at least part ofits axial length positioned within the axial length of the electricmotor, i.e. shifted into the region of the electric motor. Due to thismeasure, axial space is saved as regards the entire drive unit.

Preferably, an end portion of the wheel carrier is positioned in anannular space surrounding the gear system. In this manner, there is goodaccess possible from outside to the end portion of the wheel carrier. Itis preferred to have a face end of the wheel carrier arranged within theaxial dimension of the gear system. It is particularly expedient whensaid face end of the wheel carrier is set back with respect to the endof the axial dimension of the gear system, at best to such an extentthat a component (in particular a tire rim or a chain wheel) to bedriven by the wheel carrier may be attached there, without mountingparts projecting beyond the axial length of the gear system.

The wheel carrier preferably has a tire rim, in particular a standardrim, attached thereto. The tire rim may have a tire mounted thereon. Onenow is confronted with a more complete drive unit consisting in essenceof wheel carrier, rim, tire, electric motor and gear system. It ispreferred that this more complete wheel drive unit or the drive unitaccording to the invention described hereinbefore can be unmounted from,and mounted to, the vehicle in the form of an overall unit. Preferably,use is made of a vehicle rim that is axially split into two parts, withthe splitting thereof being preferably effected nearer to the sidefacing the vehicle center, i.e. such that the axially narrower lateralring of the rim is arranged on the rim inside.

It is emphasized that the term “wheel carrier” is not to be understoodrestrictively to the effect that the same, in operation, cogently has tobe provided with a vehicle wheel performing a rolling motion on theground or a prepared path. As a further preferred possibility, a chainwheel is cited driving e.g. a caterpillar track of a caterpillarvehicle, e.g. in case of an earth mover. An additional alternative isthe attachment of a gear wheel on the wheel carrier which, e.g. in caseof a cogwheel railway, may cooperate with a stationary toothed rack or,e.g. via rotary intermediate parts, may work on the driving wheel of amotor vehicle.

It is possible to provide the gear system either on the side of theelectric motor more remote from the vehicle center when the drive unitis in use, or on the other side of the electric motor. Thefirst-mentioned alternative is preferred since, as a rule, it leads tomore convenient attachment of the stator of the electric motor to thestub axle.

The side of the wheel carrier directed away from the gear systempreferably is provided with a brake means, with the rotatable part ofthe brake means (typically brake disc or brake drum) being joined to thewheel carrier directly or indirectly via intermediate parts. One now hasa complete drive unit comprising also a brake means, in addition towheel carrier, electric motor, gear system, optionally wheel rim,optionally tire.

It is possible in many embodiments of the invention to rigidly couplethe output of the gear system and the wheel carrier. However, there areembodiments in which it makes sense to provide a coupling between gearsystem output and wheel carrier that compensates relative motions. Theseare in particular such embodiments in which both bearings of the wheelcarrier are provided on one side of the gear system on the stub axle, asrelative motions between gear system and wheel carrier arise here moreeasily due to the principle employed or since it is more likely ingeneral that, due to manufacturing processes, minor mis-positioningresults in the relation between gear system output and the couplingregion of the wheel carrier to the gear system.

Couplings compensating relative motions may be preferably a curved teethcoupling or an elastic mechanical coupling or a torque transmission tubefixed on one side and having a tolerance-compensating toothingarrangement.

In accordance with a preferred development of the invention, areleasable connection is provided in the torque transmission pathbetween the electric motor and the gear system. Practical use of a motorvehicle equipped with at least one drive unit according to the inventionis considerably facilitated when, in particular for towing the vehiclewith the aid of another vehicle or for continuing the ride in case of adefective electric motor, the gear system indeed rotates along, withouthowever the rotor of the electric motor cogently rotating as well. Thereleasable connection does not need to be located in front of the inputof the gear system in the strict sense. It may also be located betweentwo gear system components. However, it is expedient if it is arrangedat least close to the gear system input, where torque increase has notyet taken place. In terms of design, it is preferred to provide thereleasable connection radially inside of the support of the rotatablegear system part connected to the wheel carrier.

It is altogether preferred to incorporate the releasable connection intothe gear system. It is preferred that the releasable connection isdesigned to be releasable from the outside. The releasable connectionmay be provided such that it may be released while the vehicle isstopped; however, it is particularly expedient to design the releasableconnection such that it is releasable while the vehicle is in motion.

According to a preferred development of the invention, there is provideda plug system for connecting the electric motor electrically and interms of cooling. This is the preferred alternative with respect to aconnection by means of lines—which is possible as well in the scope ofthe invention—that cannot be mated and unmated by means of plugs. Theelectrical connection involves the supply of electrical energy for thedriving motor function, optionally the discharge of electrical energy(when the electric motor is utilized in a braking function as well), inmany cases electric control connections (in particular when anelectronic control of the electric motor is arranged within thevehicle), and in many cases electrical connections to sensors in theregion of the drive unit. The connection in terms of cooling, as a rule,involves a line or a line path for cooling fluid (liquid or gaseous) forcooling the electric motor. In addition to the connections mentioned,there may preferably be provided additional connections that areestablished via the plug system. In this context, reference is to bemade in particular to connecting lines for a wheel pressure regulatingsystem and/or a rotational speed sensor on the wheel side, moreover aconnection in terms of cooling for the transmission oil. The possibilityof a line for venting the gear system or for operating the releasableconnection between gear system should be mentioned as well.

As regards the lines between the drive unit and the remainder of thevehicle (i.e. normally the vehicle interior), there are two philosophiespossible: on the one hand, the philosophy of combination, so as toarrive at a common enclosure for all lines between the drive unit andthe remainder of the vehicle, and on the other hand the philosophy ofsplitting the lines, to a larger or lesser extent, to several linestrands. In case of the first philosophy, mounting and unmounting areparticularly simple; in the event of defects, however, usually theentire, united line strand has to be replaced. In case of the secondphilosophy, the mounting expenditure indeed is somewhat higher, butthere are thinner and more flexible line strands involved, permittingmore freedom in conductor or line strand routing. When a plurality ofline strands is present, it is preferred to provide separated linestrand routing schemes on or in different parts of the wheel suspensionof the vehicle wheel concerned. In this regard, the parts of the wheelsuspension, which possibly are dimensioned differently, may be used incorresponding manner for line strand routing. According to a developmentof the invention, it is possible to provide the lines in partlyredundant manner, so that, in case of failure of one of several linestrands, there is still available a sufficient number of operativestator windings, sufficient cooling etc., be it for a reduced motorpower.

Making use of one common line strand for all lines does not cogentlymean that the plug system consists of one single, matable pair of plugunits, although this is one of the technically feasible possibilities.However, it is possible as well to provide several pairs of matable plugunits, e.g. one or more pairs of electric plug units and one or morepairs of fluid-type plug units. In case of several line strands, theremay be provided one pair of plug units for each line strand; however,this is not cogent, but other distributions and combinations of thepairs of plug units are possible as well. Reference is made to thefollowing preferred features of the plug system or plug units,respectively: one or more foremost guide pins, floating arrangement inparticular of smaller contact pins (e.g. for sensor connections) oncommon carrier, self-sealing couplings for liquid and, optionally,pressurized air.

The electric motor of the drive unit preferably may be operated as abrake, thus operating in a generator mode. The electric motor or motorsof all drive units of the motor vehicle (together) may constitute themain service brake of the motor vehicle. The mechanical brake meansmentioned further above may be the main service brake or a supportingservice brake in addition to the electric motors, or just a parkingand/or emergency brake.

The electric motor preferably is designed with permanent-magneticexcitation on the rotor. Such electric motors can be designed withparticularly high power density, which is very advantageous in the lightof the space conditions in case of the drive unit according to theinvention. The electric motor preferably is formed with an externalrotor. Such motors can be built with particularly high power density andwith particularly high torque, as measured in relation to volume orweight. These features constitute good prerequisites for integration inthe drive unit according to the invention.

A further subject matter of the invention is a wheel drive unit for amotor vehicle, comprising:

(a) an electric drive unit as disclosed in the present application;

(b) and a motor vehicle wheel mounted on the wheel carrier of the driveunit.

This wheel drive unit is a component which can be unmounted from themotor vehicle and mounted to the motor vehicle in the form of a unit. Inaddition to the mechanical attachment, merely the electrical connectionsand the connections in terms of cooling need to be established, inparticular by a plug system.

Preferably the drive unit, if desired except for a partial region of thestub axle component on the vehicle side, and preferably inclusive of abrake disk or a brake drum, is accommodated substantially within theaxial dimension of the motor vehicle wheel. Or in other words: the thusdefined drive unit is substantially not wider in axial direction thanthe motor vehicle wheel and in essence does not project axially beyondthe wheel on any of the two wheel sides.

The wheel drive unit preferably has at least one mounting portion whereit is adapted to be mounted on a wheel suspension of the motor vehicle.This may be connecting locations for suspension-arm-like components ofthe wheel suspension, but also a design of the stub axle component inthe form of a component of the type of a steering knuckle, so that theentire wheel drive unit may be pivoted for steering the motor vehicle.

Still another subject matter of the invention is a motor vehiclecomprising at least one drive unit as disclosed in the presentapplication or at least one wheel drive unit as disclosed in the presentapplication.

The motor vehicle equipped with the drive unit according to theinvention or with the more complete wheel drive unit according to theinvention, may be a motor vehicle in which steering of the wheels of oneaxle only is possible. However, it may also be a vehicle in whichsteering of the wheels of two axles or of the wheels of still more axlesis possible. It may also be a vehicle in which steering of the wheels ofall axles is possible.

The invention and preferred developments of the invention will bedescribed in more detail hereinafter by way of embodiments illustratedin the drawings, in which

FIG. 1 shows an axial longitudinal sectional view of a first embodimentof a wheel drive unit;

FIG. 2 shows a cutout of FIG. 1 in an enlarged scale;

FIG. 3 shows an axial longitudinal sectional view of a second embodimentof a wheel drive unit;

FIG. 4 shows an axial sectional view of a bipartite tire rim.

The wheel drive unit 2 illustrated in drawing FIG. 1 contains thefollowing main components:

-   -   stub axle component 4,    -   wheel carrier 6,    -   stator 8 of an electric motor 22,    -   rotor 10 of electric motor 22,    -   gear system 12 in the form of a planetary gear system,    -   wheel rim 14,    -   tire 16,    -   brake means 60.

By removing the wheel rim 14 along with the tire 16 from the thusdescribed wheel drive unit 2, one arrives at a drive unit 3 according tothe invention, comprising the main components wheel carrier 6, electricmotor 22, gear system 12, brake disc 86.

The stub axle component 4, which will be briefly referred to as stubaxle 4 in the following, is of larger diameter in its left-hand portionin FIG. 1 and of smaller diameter in its right-hand, axially longerportion. On the larger diameter portion, there is arranged a firstbearing 18 of the wheel carrier 6, which in the present embodiment is aball bearing.

The wheel carrier 6 in its entirety—roughly speaking—is cup-shaped andconsists of a—roughly speaking—disc-shaped first part 6 a and asubstantially cylindrical part 6 b.

At the diameter transition from larger diameter portion of stub axle 4to the smaller diameter portion, the stub axle 4 has a mounting ring 20attached thereto. The mounting ring 20 has the stator 8 of the electricmotor 22 attached thereto. On its left-hand end face in FIG. 1, thestator 8, except for the radially outer portion of the same, is axiallysomewhat recessed, so that the first bearing 18 of the wheel carrier 6extends a certain distance into the axial dimension of the electricmotor 22.

The rotor 10 of the electric motor 22 is cup-shaped, with the cup beingopen towards the left-hand side in FIG. 1 and the central portion havingthreadedly mounted thereon a sleeve-shaped lug 24 projecting towards theleft. Two axially spaced ball bearings 26 of the rotor 10 are positionedbetween a sleeve-like extension 28 of mounting ring 20—radiallyinside—and the lug 24—radially outside.

The design of the torque-transmitting connection between rotor 10 andgear system 12 will not yet be described here. The gear system 12, inthe instant case in the form of a one-stage planetary gear system,adjoins the electric motor 22 on the right-hand side in FIG. 1. The gearsystem 12 comprises as main component parts of the same a rotatablydriven sun wheel 30, a rotatably supported planet carrier 32, aplurality of circumferentially distributed planet wheels 34 arranged inthe planet carrier 32 for rotation of their own, as well as aninternally toothed ring gear 36 fixed on the stub axle 4 innon-rotatable manner. The sun wheel 30 meshes with a first toothedportion 38 of the respective planet wheel 34. Axially beside the firsttoothed portion 38, each planet wheel 34 has a second toothed portion 40on a smaller diameter, which meshes with the inner toothed portion 42 ofring gear 36, so that a stepped planet wheel is formed. The transmissionoutput of the gear system 12 is the planet carrier 32 which, in theregion of the outer circumference of the same, is threadedly attached tothe, in FIG. 1, rightwardly directed end face of the cylindrical part 6b of wheel carrier 6. Towards the right in FIG. 1, the gear system 12and thus the entire drive unit 3 is confined by a two-part cover 44.

The ring gear 36 consists in essence of an annular internally toothedportion 46 and a main body 48—threadedly attached thereto—having asubstantially cylindrical central portion 50 and a middle portion 52extending from the central portion radially towards the outside. Centralportion 50 is positioned on stub axle 4 and fixed there so as to benon-rotatable. Planet carrier 32 is rotatably supported, by means of abearing 54—in the instant case a roller bearing—, on the intermediateportion 52 of ring gear 36. Due to the fact that planet carrier 32 isthreadedly attached on its outer circumference to wheel carrier 6,bearing 54 constitutes a second bearing of wheel carrier 6. This bearing54 thus has the double function of supporting the planet carrier 32 ofgear system 12 and of supporting, indirectly, also the wheel carrier 6,in extremely space-saving manner within gear system 12. The firstbearing 18 and the second bearing 54 of the wheel carrier 6 are spacedfrom each other by a desirably large axial distance.

The torque-transmitting connection between the rotor 10 of the electricmotor 22 and the transmission input of the gear system 12 will bedescribed now by way of FIG. 2. Rotor 10 has a central bore 62 which isof somewhat larger diameter than the right-hand portion of stub axle 4.In this region, rotor 10 has a ring 64 threadedly attached thereto whichprojects radially towards the inside. In the inner bore thereof, ring 64is provided with an axially extending multi-groove toothed portion 66.In addition thereto, a sleeve-like toothed ring 68 can be seen having anexternally toothed portion 70 in a region located slightly towards theright from the center. This externally toothed portion 70 meshes withthe toothed portions 38 of the several planet wheels 34 so that thetoothed ring 68 constitutes the sun wheel of the planetary gear system12. In the left-hand end portion in FIG. 2, the toothed ring 68 has anexternal multi-groove toothed portion 72. This external multi-groovetoothed portion 72 is fitted into the already described innermulti-groove toothed portion 66 of ring 64. It is to be understood thatthe multi-groove toothed portions 66 and 72 are worked in such exact andmutually matching manner that good centering of the toothed ring 68 inrotor 10 is ensured.

In the following, a description will be given as to how theafore-described torque-transmitting connection between rotor 10 and gearsystem 12 can be released or canceled. The toothed ring 68, in theright-hand end portion of the same in FIG. 2, has an outer peripheralgroove in which a split ring 74 (not visible in the drawing) engagesfrom the outside. Distributed over its circumference, ring 74 has aplurality of threaded bores, with a threaded bolt 76 extending througheach thereof. When all bolts 76 are rotated simultaneously, ring 74 isdisplaced, in the manner of a traveling nut, in axial direction of thedrive unit 3, towards the left in FIG. 2. In doing so, ring 74 entrainstoothed ring 68 towards the left, with the toothed ring 68 being ablewithout any problem to shift towards the left because of the pair ofmulti-groove toothed portions 66 and 72. This shifting or displacementmotion continues until toothed portion 70 of toothed ring 68 isdisengaged from the respective toothed portion 38 of the respectiveplanet wheel 34. In this state, the torque transmission from the sunwheel of the planetary gear system 12 to the planet wheels 34 of gearsystem 12 is interrupted. By rotating the threaded bolts 76 in theopposite direction, engagement between the sun wheel and the planetwheels 34 can be restored. The possibility of releasing or interruptingthe torque-transmitting connection between electric motor 22 and gearsystem 12 is advantageous when the motor vehicle equipped with one ormore wheel drive units 1 according to the invention is to be towed orwhen the electric motor 22 of one of several wheel drive units 2 isdefective, while however driving of the vehicle is to be continued usingthe electric motor 22 of at least one other wheel drive unit 2.

It is emphasized that, in spite of the simple mechanical designdescribed, using threaded bolts 76, it is also possible to provide formore highly mechanized solutions. As an example, the provision of ahydraulic or pneumatic ring piston is to be indicated, which acts on thetoothed ring 68. Such a solution, as well as other possible solutions,may easily be provided such that release of the torque-transmittingconnection between electric motor 22 and gear system 12 is possiblewithout any unmounting work and even while the vehicle is in motion. Thehydraulic liquid or the pressurized air for effecting opening/closing ofthe torque-transmitting connection may take place by means of lines inthe interior of the stub axle 4, making a bend radially towards theoutside on the right-hand face end in FIG. 2.

FIG. 2 clearly reveals furthermore the cylindrical central portion 50 ofring gear 36 as well as the second bearing 54. Ring gear 36 is clampedaxially against the extension 28 of the mounting ring 20 for the stator8 of the electric motor 22, by means of a pressing ring 78 threadedlyattached to the right-hand face end of stub axle 4. Ring gear 36,pressing ring 78 and extension 28 are all fixed to stub axle 4 innon-rotatable manner.

Furthermore, FIG. 2 clearly shows how a supporting bolt 80 for a planetwheel 34 (there are several supporting bolts 80 and planet wheels 34distributed over the circumference) is mounted in the planet carrier 32in non-rotatable and axially non-displaceable manner. The supportingbolt 80 has the respective planet wheel 34 rotatably mounted thereon bymeans of needle bearings 82. The toothed portion 40 of planet wheel 34meshes with the internally toothed portion 42 of ring gear 36.

In the inside, the gear system 12 is filled with transmission oil. Shaftseals 84 provide for sealing of the gear system 12 on the left-hand endand on the right-hand end.

Returning to FIG. 1, the brake means 60 will be described in more detailnow. In the present embodiment, brake means 60 comprises a brake disc 86threadedly attached, from the left, to a mounting face of the wheelcarrier 6, as well as a plurality of brake calipers 88 distributed overthe circumference of the brake disc 86. The brake calipers 88 containbrake pistons and brake pads (not shown). There may be providedhydraulically, pneumatically and electrically operated brakes.

Finally, FIG. 1 shows wheel suspension parts 90 by means of which theentire wheel drive unit 2 is attached to a vehicle in an operativestate. The wheel suspension parts 90 are threadedly attached to one ormore leftwardly directed mounting faces of the stub axle component 4.

Finally, FIG. 1 reveals a plug unit 92 located centrally and coaxiallyin a face-side recess of the stub axle 4 on the left-hand side of thesame. Plug unit 92 has, on a diameter in circumferentially distributedmanner, a plurality of electric plug pins (in particular for supplyingelectrical energy to the windings of stator 8, for transmitting signalsbetween drive unit 3 and vehicle, e.g. rotary position sensor of theelectric motor 22, sensors for temperatures inside electric motor 22 andinside gear system 12, sensor for tire pressure, speed sensor foranti-blocking system of brake device 60), as well as a plurality ofplug-pin-like hollow connection pieces for carrying a fluid (inparticular cooling water or cooling oil for stator 8, transmission oilcooling). The counter or mating elements for all plug pins are providedon the supporting ring 20 and project from there through correspondingopenings in the stub axle component 4 towards the left in FIG. 1. In thesolution illustrated, there is only one plug unit 92. As an alternative,a plurality of plug units 92 could be utilized.

As an alternative, the counter or mating elements mentioned could bepositioned on the stub axle component 4. Another modification consistsin positioning said plug pins on the supporting ring 20 or the stub axle4, and positioning said counter elements on “plug unit” 92. It is alsopossible to arrange part of the plug pins on plug unit 92 (and to thenmount the counter elements for these plug pins on the supporting ring 20or the stub axle) and to arrange the remainder of the plug pins on thesupporting ring 20 or the stub axle 4 (arranging the counter elementsfor these plug pins on “plug unit” 92). Finally, a modification is to bementioned in which an intermediate plug unit is positioned on the stubaxle component 4 (leftwardly directed: only plug pins or in part plugpins and in part sockets or only sockets; rightwardly directed: onlyplug pins or in part plug pins and in part sockets or only sockets),with the respective appropriate counter elements being provided on theleft-hand side on the plug unit 92, and the respective appropriatecounter elements being provided on the right-hand side on the supportingring 20.

FIG. 1 shows furthermore that all necessary lines (for current, signals,liquids, optionally gases) extend from plug unit 92 in the form of acommon line strand in a common enclosure 94, typically into the interiorof the motor vehicle having the wheel drive unit 2 mounted thereto. Theline strand, along with the enclosure 94, is flexible so that the wheeldrive unit 2 may perform steering motions, motions due to vehiclesprings and optionally additional motions in relation to the remainderof the vehicle. As an alternative, it is possible to distribute thelines to several line strands.

FIG. 1 shows that the left-hand outside of the left-hand limit of tire16 and the right-hand outside of the right-hand limit of tire 16 markthe axial width of the wheel drive unit 2 in its entirety (cf. confininglines 96). The wheel carrier 6, the brake disc 86 (however, not thebrake calipers 88 in their entirety), the electric motor 22 and the gearsystem 12 are located substantially within this axial dimension 96-96.The, in FIG. 1, right-hand side of the wheel drive unit 2 is directedaway from the center of the motor vehicle and the, in FIG. 1, left-handside of the wheel drive unit 2 is directed towards the center of themotor vehicle to which the wheel drive unit 2 is to be, or is, mounted.

By releasing the bolts 98 or nuts, the rim 14 together with the tire 16may be removed from the wheel drive unit towards the right-hand side,completely analogous to a conventional motor vehicle with mechanicallydriven wheel. The screw heads or nuts 98 are also located within theaxial width 96-96. Upon unmounting of the rim 14 along with the tire 16,the entire gear system 12 can be unmounted. To this end, it is merelynecessary to remove the cover 44 and to remove the pressing ring 78 aswell as bolts 100 between the planet carrier 32 and the wheel carrier 6;the entire gear system 12 may then be pulled out axially towards theright, thus moving toothed ring 68 out of the ring 64. The secondbearing 54 is removed along with the gear system 12. In unmounting thegear system 12 it is possible either to remove the cylindrical part 6 bof wheel carrier 6 or not to remove the same along therewith. Withcorresponding load dimensioning of the bearing 18, the gear system 12may also be unmounted without prior removal of the rim 14 towards theright.

As an alternative, the rim 14 can also be unmounted together with thegear system 12.

Upon unmounting of the gear system 12, the electric motor 12, inclusiveof its mounting ring 20 with extension 28 from stub axle 4, may now beaxially pulled out towards the right in FIG. 1. The plug-typeconnections with plug 92 are separated automatically in doing so.

In case the main components of the electric motor 22, rotor 10 andstator 8, are to be unmounted separately, merely bolts 99 have to bereleased first. The main part of rotor 10 then may be pulled outaxially, with the supporting portion with lug 24 remaining in the wheeldrive unit 2. However, if desired, it is also possible to remove thestator 8 towards the right, upon release of its threaded attachment tomounting ring 20; the inner diameter of the stator is dimensioned suchthat it can be moved past lug 24.

It is possible for maintenance and repair works to remove the plug unit92 from the wheel drive unit 2 towards the left.

With respect to the embodiment illustrated in FIG. 3, only thosedifferences from the embodiment of FIGS. 1 and 2 will be explained thatare of greater relevance to the invention. The same reference numeralsas before will be used for analogous component parts.

The wheel carrier 6 now is supported on the stub axle component 4 with afirst bearing 18 and a second bearing 102, with both bearings 18 and 102being provided in FIG. 3 on the left-hand side of electric motor 22. Orin other words: the central hub 104 of wheel carrier 6 is axiallywidened towards the left and now offers space for both bearings 18 and102; there is no right-hand side second support of the wheel carrier 6within the gear system 12.

The stub axle component 4 is integrally extended towards the left andpresents there two mutually aligned bores 106 for attaching the wheeldrive unit 2 to the motor vehicle. This may be in the form of a pivotalmounting for steering system pivotal motions.

The electric motor 22 is substantially of analogous design to the firstembodiment. The gear system 12, as in case of the first embodiment, is aone-stage planetary gear system illustrated in schematic outline only.The gear system 12 substantially is of analogous design to the firstembodiment; however, scarcer dimensioning in particular of bearing 54may be chosen as the gear system 12 does not have to dissipatesupporting forces for wheel carrier 6.

For torque transmission from the gear system 12 to wheel carrier 6 andto wheel rim 14, respectively, there is provided a relativelythin-walled tube 108. Torque transmission from gear system 12 to tube108 is effected by a toothed portion 110 of such design that relativemotions between gear system or transmission output and wheel carrier 6can be compensated.

It is emphasized that the gear system 12 does not necessarily have to bedesigned with transmission output from the planet carrier 32. As analternative, it is also possible to employ a transmission output fromring gear 36 and a fixed planet carrier 32. This holds for allembodiments.

In the second embodiment, wheel carrier 6 is not split axially. Theconnection between wheel carrier 6 and rim 14 is located approximatelyin the axial middle of the wheel drive unit 2. It is to be understoodthat sufficient space has to be present between the tube 108 and theouter periphery of gear system 12 in order to access mounting bolts ofwheel rim 14.

Instead of the brake disc 86, the second embodiment has a brake drum 112secured to wheel carrier 6. Operation of the brake pads in brake drum112 is effected hydraulically or pneumatically or electrically.

In each of the embodiments illustrated, the electric motor 22 isprovided with an external rotor 10 having permanent magnets ofalternating polarity (not shown) on its cylinder face directed towardsthe inside. The stator 8 is provided with poles (not shown) havingwindings thereon on its outer circumferential face. The air gap ofelectric motor 22 is cylindrical. The electric motor 22 iselectronically commutated. The electronics system arranged within thevehicle and feeding electric motor 22 is designed to switch the electricmotor 22 to generator-mode of operation so that the same operates as abrake. The electrical energy thus generated may either be fed back to acurrent line or may be supplied to an accumulator or may be converted toheat in brake resistors.

FIG. 4 illustrates the axially bipartite design of rim 14 with theaxially narrower lateral ring 120 being closer to the vehicle center. Inaddition thereto, the drawing also shows parts of the tire pressureregulating system 122 arranged on the outside.

1. An electric drive unit for a motor vehicle, comprising: (a) a stubaxle; (b) an electric motor having a stator that is fixed with respectto the stub axle and having a rotor that is rotatably supported withrespect to the stub axle; (c) a gear system having its input connectedto the rotor for torque transmission; (d) a wheel carrier connected tothe output of the gear system for torque transmission; (e) a firstbearing of the wheel carrier provided on a first axial side of theelectric motor facing away from the gear system; (f) a second bearing ofthe wheel carrier provided either on the first axial side of theelectric motor as well or in the gear system, realized in the form of abearing of a rotatable gear system part connected to the wheel carrier.2. The A drive unit according to claim 1, wherein the gear system is aplanetary gear system having a sun wheel, planet wheels, a planetcarrier and a ring gear.
 3. A drive unit of according to claim 2,wherein said bearing of a rotatable gear system part is a bearing of theplanet carrier.
 4. The drive unit of claim 2, wherein the planetary gearsystem is a planetary gear system with stepped planet wheels.
 5. Thedrive unit of claim 1, wherein a common lubricant is provided for thegear system and said bearing of a rotatable gear system part.
 6. Thedrive unit of claim 1, wherein the rotor of the electric motor and theinput of the gear system are connected to each other withoutintermediate compensating member.
 7. The drive unit of claim 1, whereinthe wheel carrier is of axially split design.
 8. The drive unitaccording to any of claim 1, wherein the gear system is adapted to beunmounted from the drive unit in the form of a module.
 9. The drive unitof claim 7, wherein the gear system module is adapted to be unmountedtogether with a wheel carrier part.
 10. The drive unit of claim 1,wherein the main part of the rotor of the electric motor, upon releasethereof from its supporting portion, is adapted to be unmounted from thedrive unit in axial direction.
 11. The drive unit of claim 1, whereinthe stator of the electric motor is adapted to be unmounted from thedrive unit in axial direction.
 12. The drive unit of claim 1, whereinthe first bearing of the wheel carrier is positioned with at least partof its axial length within the axial length of the electric motor. 13.The drive unit of claim 1, wherein an end portion of the wheel carrieris positioned in an annular space surrounding the gear system.
 14. Thedrive unit of claim 1 wherein a face end of the wheel carrier is locatedwithin the axial dimension of the gear system.
 15. The drive unit ofclaims 1, wherein the wheel carrier has a tire rim attached thereto. 16.The drive unit of claim 15, wherein the tire rim is of bipartite design.17. The drive unit of claim 16, wherein the lateral ring of thesplittable rim is located closer to the vehicle center.
 18. The driveunit of claim 1, wherein the wheel carrier has a chain wheel attachedthereto.
 19. The drive unit of claim 1, wherein the gear system isadapted to be positioned on the vehicle outer side of the drive unit.20. The drive unit of claim 1, wherein a brake disc or a brake drum isprovided on the side of the wheel carrier facing away from the gearsystem.
 21. The drive unit of claim 1, wherein between the output of thegear system and the wheel carrier there is provided a couplingcompensating relative movements.
 22. The drive unit of claim 21, whereinthe coupling is a curved teeth coupling.
 23. The drive unit according toclaim 21, wherein the coupling is an elastic mechanical coupling. 24.The drive unit of claim 21, wherein the coupling is atorque-transmitting tube.
 25. The drive unit of claim 1, wherein areleasable connection is provided in the torque-transmitting pathbetween the electric motor and the gear system.
 26. The drive unit ofclaim 25, wherein the releasable connection is integrated in the gearsystem.
 27. The drive unit claim 25, wherein the releasable connectionis adapted to be released from the outside.
 28. The drive unit of claim1, wherein there is provided a plug system for connecting the electricmotor electrically and in terms of cooling.
 29. The drive unit accordingto claim 28, wherein the plug system contains at least one additionalconnection, preferably to at least one of a tire pressure regulatingsystem and a rotational speed sensor on the wheel side and for a gearsystem cooling means.
 30. The drive unit of claim 1, further comprisingall lines between the drive unit and the remainder of the vehicle,wherein all of said lines extend in a common, flexible enclosure. 31.The drive unit of claim 1, further comprising several line strandsprovided between drive unit and the remainder of the vehicle, each linestrand containing one or more lines.
 32. The drive unit of claim 31,wherein there are provided separated line strand routings for the driveunit, on different parts of the wheel suspension of the vehicle wheelconcerned.
 33. The drive unit of claim 1, wherein the electric motor isadapted to be operated as a brake.
 34. The drive unit of claim 1,further comprising a brake associated therewith that is designed as aparking brake.
 35. The drive unit of claim 1, wherein the electric motoris designed with permanent-magnetic excitation on the rotor.
 36. Thedrive unit of claim 1, wherein the electric motor is designed with anexternal rotor.
 37. A wheel drive unit for a motor vehicle, comprising:(a) an electric drive unit of claim 1; (b) and a motor vehicle wheelattached to the wheel carrier of the drive unit.
 38. The wheel driveunit of claim 37, wherein the drive unit, if desired except for apartial region of the stub axle component on the vehicle side, isaccommodated substantially within the axial dimension of the motorvehicle wheel.
 39. The wheel drive unit of claim 37, further comprisingat least one mounting portion where said wheel drive unit is adapted tobe attached to a wheel suspension of the motor vehicle.
 40. A motorvehicle comprising at least one electric drive unit of claim 1.